In a conventional multiplexing apparatus, priorities in multiplexing operations are determined based upon values obtained by weighting delay times occurred in multiplexing buffers in accordance with each of media sorts, and encoded units are selected from buffers having higher priorities so as to multiplex the selected encoded units with each other (refer to, for instance, Patent Document 1).
In this type of conventional multiplexing apparatus, only the priorities among the media are merely considered, so that the priority cannot be changed for each of the encoded units within the same media. In particular, in such a case that there are an important portion and a less important portion within the media, such a function capable of applying a priority with respect to each of the encoded units is required.
On the other hand, there is another multiplexing apparatus that while a priority is applied in the unit of an encoded unit, only such an encoded unit having the highest priority is transmitted (refer to, for instance, Patent Document 2).
However, in this type of multiplexing apparatus, although the priority is applied to each of the encoded units, permission/non-permission of a transmission is determined by comparing encoded units of the same timing with each other. As a result, even when encoded units having a plurality of high priorities are collected at the same timing, only one encoded unit may be merely outputted. Thus, in order to realize an effective multiplexing control operation, such a function is required by which encoded units having high priorities are outputted even if the encoded units are delayed in some degree.
Patent Document 1: JP 2000-209177 A
Patent Document 2: JP 08-279835 A